Field
Embodiments described generally relate to methods for securing a shrinkable film to a paperboard substrate and methods for making paperboard containers therefrom.
Description of the Related Art
Paperboard is used to make a wide variety of paper products, such as plates, bowls, and cups. Paper products may be insulated in a variety of ways to provide an insulated product, such as an insulated cup for hot or cold beverages. For example, the paper product may be insulated by forming an air gap within a sidewall of the container. The air gap, for example, may be located between a film that forms an inner surface of the sidewall and a paperboard substrate that forms an outer surface of the sidewall. The film may be a shrinkable film that may shrink, e.g., a heat shrinkable film, to form the gap between the film and the paperboard substrate as the film shrinks.
Typically the paperboard blank that the shrinkable film is adhered to includes an outer and an inner coating of low density polyethylene or other polymer. When a composite structure includes paperboard and a shrink film to form an insulated container, a potential defect is that a shrink force induced by the shrink film may cause delamination within the paperboard component of the substrate. The layer of paperboard fibers which are adhered to the shrink film are peeled away as the film shrinks, producing an effect generally referred to as “peel back.” Once the film peels back, the paperboard fibers are exposed and will begin to absorb liquid, e.g., coffee, if present in the container. The absorption and migration of the liquid into the paperboard blank used to form the container is generally referred to as “edge wicking.” The absorption of the liquid may reduce the structural integrity of the paperboard blank, is not aesthetically pleasing, and is generally undesirable.
There is a need, therefore, for improved methods for securing a shrinkable film to a paperboard substrate and methods for making paperboard containers therefrom that have a reduced degree of peel back of the shrinkable film along an inner sidewall seam thereof.